Structures involving particles or mineral granules treated with organic silicon compounds and method of making



Patented May 6, 1952 STRUCTURES INVOLVING PARTICLES R MINERAL GRANULES TREATED WITH OR- GANIC SILICON COMPOUNDS AND METH- OD OF MAKING Howard B. Keene and Douglas A. Anderson, St. Paul, and Paul H. Aldrich, Minneapolis, Minn., assignors to Minnesota Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware No Drawing. Application November 24, 1954, Ser al 565 054 This invention relates to the provision of organophilic surfaces on normally hydrophilicmorganic or mineral particles, which is important, for example, in providing or effecting adhesion between such particles and organophilic plastic bonding materials. This invention further concerns the provision of surface treatments which are effective in providing such organophilic surfaces on inorganic or mineral particles even when surfaces of the latter contain substantial amounts of water-soluble material. As a specific example of. an especially contemplated material, having a hydrophilic. surface and which it is desired to bond by means of an organophilic plastic bondlug materia o ored, r ofin granul s may b mentioned.

.-ln.'the production of, bituminous roll roofing and. asphalt shingles, for example, colored surface coated roofing granules are commonly applied,

as, a layer or coating, to the heated asphalt-impregnated and -coated fibrous base sheet material, and pressed into place by means of rollers. Water is then normally sprayed over the sheet so as to cool and harden the asphalt preparatoryto cutting and packing of the finished roofhydroph lic. thatwis. muchm r re w b by water than by asphalt or hydrocarbon oils. During the spray cooling operation, and also underthe action of rainfall when the roofing is later first placed in use, the water forms a film around each individual granule, and, unless the granule is very firmly and effectively bonded to the asphalt, tends to break the bond between the, granule and the asphalt, and to permit the ready disengagement of the granule from the asphalt surfaced'sheet or shingle, especially upon impac o ha l stones .orwhen workmen or even squirrels, orthe like, walk on the roof.

.To meet. this difficulty attempts have been made to pre-fcoat the granules with various organophilic materials. Hydrocarbon oils, such as slate oil," normally applied as a lubricant and anti-dust coating, are ineffective in changing the deeper embedding of the granule, and coneque flv; s t m r secure anchora e thereof, in the asphalt bond.

with a water-soluble potentially reactive phenolaldehyde resinous material which is later heatreacted to the insoluble stage to form an oriented organophilic surface coating. In thisoonnection,

i 16 Qlainis. (CL 117-27) .2 'ing. ,All mineral substances commonly used in the product on of roofin ranu es. are natu a l character of the granule surface, although they do soften the adjacent asphalt and thus permit to Hydrophilic granules have also been treated with dimethyl dichlorosilicane in. vapor 1 m gauges, and the like.

1 an as a gene al r ere c to. prio art. notch-2S- Pate t N 2,l 4,3 f an d J 3 1 G-Iifior Q Jewett- The o ganophilic s'u aio ynmduced by this means is much more readily'wet by asphalt than by water, and accordingly water does not penetrate and break the bond between granule and asphalt in the finished roof;- ing. Furthermore, the coating is, of insufficient thickness to alter the appearance of the thus treated granule.

Natural mineral granules, and ingeneral the high-temperature ceramic glaze coated granules, have thus previously been successfully provided with an organophilic surface; and correspondingly more permanent bonding between such granules and asphalt has thereby been made possible.

According to the newer practice artificial colored roofing granules having improved range and intensity of colors, made with heat-sensitive organic pigments by various low-temperature processes, have tended to replace the older materials. Manyof the newerlow-temperature coatings or glazes have been found to be slightly water-soluble, i. e, to contain small percentages of ,water-soluble materials;- and it has been found that under such conditions treatment with a phenolic resinis impossible or, at best; highly unsatisfactory, Even where such resinmay be successfully applied to the granule and reacted to the insoluble stage, the organophilic phenolaldehyde resin surface coating is not permanent, but rapidly becomes'i-neffective on exposure of the treated granule or the coated shingle to water.

It has now been found that various inorganic surfaces, which may contain small but significant amounts of water-soluble materials, and which are normallyhydrophilic in character, may be made permanently organophilic, as well as Wa lerrepellent, and without alteringtheir, appearance, by treatment with traces of organic silicon compounds, e g. certain substituted silicanes applied from solution in non-reactive organic solvents.

Various organic silicon compounds have heretofore been employed in forming strongly hydro phobic or water-repellent surfaces on such widely d ferent ma e ials as c llulose, metals, sand ceramics. examp c ntact of, la ssu ces has provided a water-proofing action highly useful in connection with the visual inspectionof liquid levels in measurin'g-cyclinders, draft However, the objects so treated contained essentially no water-soluble materials; and organophilic properties were not required.

As one possible explanation for this novel property of the substituted silicanes which we have now discovered, namely, the property of forming a permanently organophilic as well as waterrepellent surface on inorganic solids containing water-soluble materials, but without intent to belimited thereto, we advance the following theory:

The surfaces of all inorganic solids normally are covered with a very thin or molecular film of water. Contact of the substituted silicane with this water results in hydrolysis of the silicane, molecular orientation of the hydrolyzed silicane with respect to the hydrophilic inorganic surface, firm bonding of the hydrolyzed silicane to the inorganic surface, and possibly subsequent polymerization or condensation of the hydrolyzed and. oriented silicane in situ to an organophilic polymer which, whether as a continuous layer or, more likely, as a number of separate points or areas. on the inorganic surface, is then in stable equilibrium with said inorganic surface. ,ence of additional water, and even gradual leaching out of the soluble salts, is then insufl'icient to Presupset the equilibrium conditions and thus to remove any significant portion of the organophilic polymer. On the other hand, the phenol-aldehyde resin coating, herein previously mentioned, even when it can be formed thereon, is in unstable equilibrium with the inorganic surface, and any disruption of this coating then results in the rapid dislodging of the entire coating on contact with water. In support of this theory, we have noted that roofing granule particles containing quite high proportions of water-soluble material when treated with the phenol-aldehyde resin are not wet by asphalt when first placed in water, whereas water is readily and completely displaced by, asphalt from the surface of similar granules treated with a silicane. In making this observation, we may use a soft 'fiux asphalt, or a mixture of hard asphalt and a hydrocarbon oil;

for example, a mixture of 135 parts of saturating asphalt of 140 F. melting point (ball and ring) with 100 parts of slate oil may be used. The granules are first placed in a beaker and covered with water. To about grams of granules are then added about 2 grams of the soft asphalt mixture. and the whole is well stirred for from twoto five minutes. The granules are then inspected, and. the percentage of those which have been completely covered with the asphalt is estimated. By means of this test, we have obtained the following results:

Per cent covered Untreated hydrophilic granules Bakelite-treated high-temperature granules 80 Bakelite-treated low-temperature granules 0 silicane-treated low-temperature granules 90-100 While vapor phase treatment of inorganic particles, e. g. roofing granules, has been found to produce useful results, we have found that at least equally advantageous results can be secured much more simply and economically by means of a liquid phase treatment, as will be more fully described in the following specific examples, in which all parts are given as parts by weight.

Example 1 In this example, an alkoxy silicane is used for the surface-treatment of low-temperature type artificial roofing granules. The granules are prepared, for example, by completely and uniformly coating parts of crushed and graded (35- mesh) mineral aggregate, such as traprock or greystone, with a suspension of 1 part chromium oxide in 6 parts of sodium silicate; pre-drying the coated granules at about 220 F. in a steamheated rotary kiln; and further drying and firing the coated granules in a rotary direct-fired kiln at 400 to 600 F. Although such treated granules are somewhat resistant to the leaching action of water, they nevertheless gradually lose a considerable portion of the surface coating on long contact with water. A further treatment may therefore be applied, which consists of spraying the granules as they come from the kiln with a dilute (5 to 8%) solution of citric acid in an amount sufficient to provide 2 to 8 pounds of acid per ton of granules. The silicate surface coating is thereby presumably converted to insoluble silica, but the resulting soluble sodium citrate, together with unreacted alkali and/or other soluble material, remains in or within the coating. Such granules have a hydrophilic surface, and obviously contain a small but appreciable amount of water-soluble material; this watersoluble portion may be removed, as by prolonged and costly leaching, but may be disregarded when using the further treatment of our invention.

The alkoxy silicane may be prepared as follows: To parts by weight of a non-volatile hydrocarbon oil, contained in a glass-lined Jacketed. reaction vessel fitted with agitator and reflux condenser, are added 195 parts of alpha-picoline, parts of silicon tetrachloride; and 148 parts of tertiary butyl alcohol. The reaction proceeds with evolution of heat, and the temperature is carried, with external heating or cooling where required, to 200 F. The batch is held at 200 F. for 15 minutes with continual agitation, and is then cooled to 90 F. and allowed to settle. The alkoxy silicane dissolved in the oil forms an upper layer, which is decanted from the solidified lower layer of water-soluble picoline hydrochloride. The product consists of the solution, in the hydrocarbon oil, of approximately 60% by weight of alkoxy silicanes, of which the major proportion is di-t-butoxy dichloro silicane, with small amounts of mono-t-butoxy trichloro silicane and/or tri-t-butoxy monochloro silicane also present. Before being applied to the granules, this product is further diluted with additional amounts of the hydrocarbon oil in the ratio of '7 parts of the 60% solution to 93 parts of oil. No. 635 oil from the Texas Company, is an example of a satisfactory hydrocarbon oil or slate oil; it has an A. P. I. gravity of 26; S. U. viscosity at 100 F. of 312, and at 212 F. of 51.5 seconds; flash test of 430 F.; fire test of 485 F.; and pour test of 20 F.

In the normal process of granule manufacture, the heat-treated granules pass from the rotary kiln to a rotary cooler, where they are cooled and also customarily treated with slate oil, before passing to storage. they enter the cooler they are sprayed with a controlled amount of water, which is then allowed to evaporate and thereby to cool the granules until, at a subsequent point in the cooler, they have reached a temperature of 170-180 F. and a moisture content of 2-5 lbs. of water per In the present example, as,'

tenet-granules. are then further sprayed with an: amount of the silicane solution sufiicient.

to provideabout-fi lbs. of'sla-te oil and correspond inglyaboutonewquarter poundof' silicane-per ton of granules, Thissolution is applied uniformly tov all granules surfaces; theremaining; moisture is removed; and the granules arecooledtgto room temperature,-; by the continuediaction of the rotary cooler. Granules so treated arefountt toibewaters repellent: and readilywet: bya'fluidqasphaltv even in the-presence o f-water-; and: they provide;- a

superior typeof product :foruse: in' the surfacing of" asphalt roofing and} the like.

:Emcmpla:

J Low --'tem'perature artifici l colored roofin ranules are prepared by coating: a, crushed; n

graded slate aggregate with a; phthalocyanine pigment in; asodium silieatebase cementingcompositionwhic'hris subsequently set. up toa. weather-lresistant. state, by reaction; at 2009490.- with a reactive fluorine-containing compound; such. as magnesiun iluosilicate. The dry. granules are. treated at about 140": F. with a solutionof, diethyl dichlorosilicane in slate oil, of sufiicient concentration and "in suflicient. amount to supply .5 lbs; of oil and lb. of silicaneper ton of granules. Uniform coating. is obtained; by tumbling" in a rotary tube such as the rotary cooler o,f;.Example 1, while cooling the granules toroom temperature The treatedgranule are organophilieand form a good bond, with asphalt evenin the-presence medium for the silicane. :Various. other volatile ,oif: no rm tile li ui is'blve ts may alsobeused butrsu h solre its must.

be. Selected soas. ot; r a t with; the sil es. S vent .ct'theet erne. c t-chlorinated; h

' chlorosi ea ud reaction products consist g oimixture oi mono-. di-;' and tri-t-amoxy chlorosilicanes; propoxyata butoxy dichlorosilicane; dichlorosilicanes; derived from. mixtures of, fusel oiland t-butyL-alcohol;

. t-butoxy-iso-amoxy dichlorosi licane; ,t-b to c-ys of water, and/or after prolonged-water extrac': tion; theti'eatment is weather resistant; abrasion resistant; and is also resistant to hydrolysis even at elevatewten' peratures.

. I JJEacmnle-S Road aggregate .1 consisting oi. crushed and graded. trap; rock is.treatedrwithflw pounds per t n f a-fiv p centsolut on-is slate. oil oi; allso y dichlorosilieanes derived from eq al, molar. n

t ns isobropyi alcohol-and tertiary-buty al-L w it comp ising a. diailkoxudich10m l c containing. substantially equal: numbers of i propoxy andit-butoxy'groups. .Thessilicanes Prepared 1g the-method descrihed-undf rlflxam l. The treated aggregajte'is found bepr g; 1 philic, has. ood adhesion to asph'altand ;p

vldes. an eliective material for use-inthe surfae-' pletely insoluble materialsmay alsobepadvana tageously tr'eated. However, thereare also, glistinct advantages to be gained inthe substitution of. our novel silicane' treatment for previously known treatments such as that. with phenolic resins. For example, road aggregate may be treated withoutsubsequent heating, as in Exa ple 3. HighFtemperatureartificialcolored 1 zed roofing :granulesmay likewise-be titeated'without additionalor prolonged hea n and .iurtherihore may be: simultaneously treated with "slate 1:1 or the" like. The silicane- -treated surfaces remain organophilic even under considerable abrasion.

One of the chief advantages of our-invention as related to the roofingv granule art lies in the application of the organophilic surfacing material methoxy dichlorosilicane; di-tvbutoxy hydroxy silicane; di-tshutoxy-dianiil'iflsi icanei aminosilicane; di-.n-.pr0py1 diehl /ii phenyl triohlorosilicanegl,nwdecyl t a 11-. cane; monoethyl trichlorosilicane anddiethyl dichlorosilicane.

In general. we haveif wmp u ds. of si i =QI1= a as tha 1,3119%; creams i; pr f red "whighh't ie ri atives or si icon is raliy r de, tfiiiHi al o known as silicane 011 silane"), in which; at least enact the hydro e is replaced byan alkyl, aryl, alkoxy r MY QXY sr up. andat l ast one. hydrogen-is replaced by ahalogen or, by an amino or hydrony group; or simple; compounds-which are obtained by intra, or inter-polymerizationof suchderivative's havin ,wo onmore amiuozor hydroxy groups. To be eiiective tor oiiirpurpo es. theorganic silicon comp 'nd :milstiha e a on up- P r i .0 tat on o .t eh ,0: philic mineral surface; nd-at; lcastaone-ygroup permitting an organophilic relationship to asphalt or the like. I

In applying the compounds of v these-various classes to the. :hydrophilic surfaces of, Tooling granules and the like, .we-find certaindiiierences in technique to bedesii able depending on-gthe particular class of compound being; applied. example, it appears toi bje' desirable to; applyaa slight amount of moistureto the granules prior to treatment with'the a oxy,clilorosilieanes as indicated in'Example 1. However, in the presence ofv water these compounds are broken down rather p dl part u ar y t elevated t mperatures; and it-therefore becomes necessaryto. lQWer, the temperature of the granules to not over F'., more or less, before applicationof the silicane solution. After treatment'it is furthernecessary to remove all moisture from the granules, and it is. also advisable to cool them to room temperature. beiore P a ng ri et ea ed anules. i tq a e, in order to; a; subsequenthydrolysis ofthe coating and consequent partial reduction of organophilic properties.

Certain differences in the granules also may affect the technique usedin applying thesilicane treatment. Thus it is sometimes desirable to add a small amount of ammonia, or, where the granule coating contains free alkali, of ammonium chloride, to the water applied to the hot granules as in Example 1, in order to provide free ammonia, the presence of which appears to have a beneficial effect in providing an improved organophilic treatment, particularly with the alkoxy silicanes.

Due, probably, to the presence of a minute film of water even 'on granules direct from the lowtemperature kiln,- it is possible in many cases to obtain organophilicproperties with the alkoxy chlorosilicanes even without the addition of water. This is ev'en more true of the alkyl chlorosilicanes, which as shown in Example -2 willproduce an organophilic'surface by application in hydrocar-= bon-solution to the heated granules as they come fromthe kiln and without intermediate moistening. The organophilic surfaces thus produced also"seem"to be somewhat more stable towards subsequent heating in the presenceof moisture thanarethe surfaces produced with the alkoxy compounds.

While we have found that resinous polymers of organic silicanes applied in a voltatile solvent and dried in place on the granules will produce beneficial results, we prefer to use the monomeric compounds, since these latter materials are effective-inconsiderably lower concentrations and do not require the evaporation of solvent in order to'establish a permanent organophilic surface. The monomeric silicanes are capable of molecular orientation on the granule prior to polymerization, whichoccurs in situ; and an effective bond between final polymer and original granule surface .is thereby more readily established. :However, dimers or other low polymers of our silicanes, which are still sufficiently mobile and re active: to establish 'proper orientation at the granule. surface also have preferred properties. In the foregoing discussion, polymerization or other similar terms refers to the apparent re action of the original silicane in forming the permanent, organophilic surface layer obtained; it' may or may not be concerned with increases in molecular weightyand accordingly we do not wish. to =be-limited to any specific theory as to the mechanics-of the formation .of "our new im proved. granule-surface. A

Hydrolysis of an organic chlorosi-licane, it will be readily appreciated, will result in the liberation-of hydrogen chloride; and this substance is actually liberated on treatment of moisture-containing granules with e. g..di-t-butoxy dichlorosiiicane. The very small amount of acid thus produced is. normally without effect on the'granul e. However, in the case of granules which are susceptible to the action of such acids, for example th'ose carrying a basic pigment which changes; color by reaction with hydrogen chloride, it may be desirable to use other types of silicanes, such as-the organic amino silicanes or the like.

What we claim is: l. The process of forming colored roofing granules having improved anchorage in asphalt coatings,"comprising: coating base granules with a colored coating composition comprising water-solubl'' sodium silicate; converting the silicate to insoluble silica at a temperature not above about 60O'"F." and withoutremoving the small but-appreciable amount. of'water-soluble material remaining after such conversion; and applying to the hydrophilic surface of the resultant granules a.thin coating of a solution in a hydrocarbon of a substitutedsilicane capable of molecular orientation with respect to a hydrophilic mineral surface, said silicane being selected from the group consisting of alkyl, aryl, alkoxy and aryloxy silicanes containing at least one readily hydrolyzable in-',

organic radical attached to silicon.

2. The process of forming colored low-temperature type roofing granules having an organophilic and water-repellent surface of such character that water in contact with said surface and at room temperature is preferentially displaced from'said surface by'soft asphalt, comprising: coating base-granules with a colored coating composition comprising water-soluble sodium silicate; converting the silicate to insoluble silica at a temperature not higher than about 600 F. and without removing the small but appreciable amount of water-soluble material remaining after such conversion; and coating the thus treated granules with a thin layer of a solution in an organic solvent of an organic silicon compound selected from the group consisting of alkyl, aryl, alko'xy and aryloxy silicanes having one to three readily hydrolyzable radicals attached to silicon.-

3. The process of claim 1 in which the substituted'silicane is diethyl dichlorosilicane.

4. The process of claim 1 in which the substituted silicane is a mixture of alkoxy chlorosilicanes consisting preponderantly of di-t-butoxy dichlorosilicane. I

5. The process of claim 1 in which the substituted silicaneis adi--alkoxy dichlorosilicane containing substantially equal numbers of isopropoxy and t-butoxy groups.

6. The process of forming colored roofing granules-having improved anchorage in asphalt coatings, comprising: coatingbase granules with a colored coating composition, comprising watersoluble sodium silicate; converting the silicate to insoluble silica at a temperature not above about 600 F. and without removing the small but appreciable amount of water-soluble material remaining after such conversion; and applying to the hydrophilic surface of the resultant granules a thin coating of a solution in liquid hydrocarbon of an organic silicon compound formed .in the aminolysis of a chlorosilicane selected from the group consisting of-alkyl, aryl, alkoxy and aryloxy silicanes-having one it'o'three chlorine atoms, at tached to silicon; I

- 7. The method-of coating a hydrophilic inorganic surface formed by coating a supporting inorganic base with a coating composition comprising water-soluble sodium silicate and then converting the silicate. to insoluble silica a-t'a temperature not above about 600? F. and without removing the small-but appreciable amount of water-soluble material remaining after such conversion, v witha t-alkoxy-substituted silicanc, which method comprises forming a t-alkoxy chloro'silicane in an organic solvent, and applying the thus formed solution to said hydrophilic inorganic surface.

8. Colored roofing granules having an organophilic. and water-repellent surface of such character that water in contact with said surface and at room temperature is preferentially displaced from said surface by soft asphalt, said granules being the product of the processof claim'l.

=9. Colored roofing granules containing water'- soluble material and produced by a process comprising coating base granules with a colored coating composition comprising water-soluble sodium silicate and then converting the silicate .to insoluble silica at a temperature not above about 600 F, and without removing the small but appreciable amount of water-soluble material released thereby, said granules having an organephilic and water-repellent surface coating of such character that Water in contact with said surface coating and at room temperature is preferentially displaced from said surface coating by soft asphalt, said organophilic surface coating comprising an organic compound of silicon having one to three organic groups, selected from the class consisting of alkyl, aryl, alkoxy and arylozry groups, per silicon atom in the molecule.

10. Mineral aggregate coated with a coating composition comprising water-soluble sodium silicate and heated to a temperature not over about 600 F. to convert the silicate to insoluble silica Without removing the small but appreciable amount of Water-soluble material remaining after such conversion, and having a water-repe1lent organophilic surface coating of such character that water in contact with said surface coating and at room temperature is preferentially displaced from said surface coating by soft asphalt, said organophilic surface comprising an organic compound of silicon in which the silicon is bonded to at least one tertiary-alkoxy radical.

l1. Colored roofing granules having an organophilic and water-repellent surface of such character that water in contact with said surface and at room temperature is preferentialy displaced from said surface by soft asphalt, said granules being the product of the process of claim 6.

12. Colored roofing granules in accordance with claim 11, in which the chlorosilicane is an alkyl chlorosilicane.

13. An artificial colored roofing granule, comprising a mineral base coated with a colored surface coating containing a small but appreciable amount of water soluble material and formed from a colored coating composition comprising water-soluble sodium silicate by converting the silicate to insoluble silica at a temperature not higher than about 600 F. and without removing the small but appreciable amount of water-soluble material remaining after such conversion, and said granule having a Water-repellent, organephilic surface of such character that Water in contact with said surface and at room temperature i preferentially displaced from said surface by soft asphalt, said organophilic surface comprising an organic compound of silicon, and said organophilic surface having been formed by applying to the initially hydrophilic colored siliceous surface a thin coating of a solution in an organic solvent of a tertiary-alkoxy amino silioane.

14. As a new manufacture, a sheet material comprising a fibrous base sheet and an adherently attached coating thereon of a water-insoluble organic film-forming binder having as a filler therein a finely divided porous inorganic particulate material the individual particles having been coated with a coating composition comprising a water-soluble sodium silicate and heated to a temperature not above about 600 F. to convert the silicate to insoluble silica and without removing the small but appreciable amount of water-soluble material remaining after such conversion, and said particles further having a waterrepellent organophilic surface coating of such character that water in contact with said surface coating and at room temperature is preferentially displaced from said surface coating by soft as phalt, said organophilic surface coating comprising an organic compound of silicon in which the silicon is bonded to at least one tertiary alkoxy radical, the aforesaid adherently attached coating thereby providing a water-repellent sheet product.

' 15, As as new manufacture, a sheet material comprising a fibrous base, an adherently attached coating thereon of a water-insoluble organic film= forming binder, and, partially embedded in said coating, the colored roofing granules of claim 8.

16. As a new manufacture, a sheet material comprising a fibrous base, an adherently attached coating thereon of a water-insoluble organic filmforming binder, and, partially embedded in said coating, the colored roofing granules of claim 11.

HOWARD B. KEENE. DOUGLAS A. ANDERSON. PAUL I-I. ALDRICH.

BEFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,030,787 Bley Feb. 11, 1936 2,030,739 Bley Feb. 11, 1936 2,061,338 Ward Nov. 17, 1936 2,118,899 Price May 31, 1933 2,164,329 Jewett July 4, 1939 2,258,221 Rochow Oct. 7, 1941 2,265,962 Bent et al. Dec. 9, 1941 2,306,222 Patnode Dec. 22, 1942 2,386,259 Norton Oct. 9, 1945 2,390,370 Hyde Dec. 4, 1945 2,412,470 Norton Dec. 10, 1946 2,432,891 Hervey Dec. 16, 194'? 2,436,304 Johannson Feb. 17, 1948 2,439,689 Hyde Apr. 13, 1948 2,455,999 Hyde Dec. 14, 1943 2,462,635 Haber Feb. 22, 1949 FOREIGN PATENTS Number Country Date 203,642 Great Britain Sept. 6, 1923 OTHER REFERENCES Kig-Journal Oil Colour Chemists Assn, vol. 13, No. 116, pp. 33-34.

Gilliam et al., Journal American Chem. Soc., March 1941, vol. 63, p. 801.

Norton General Electric Review, vol. 4, No. 8, Aug. 1944, pp. 12 and 13. 

1. THE PROCESS OF FORMING COLORED ROOFING GRANULES HAVING IMPROVED ANCHORAGE IN ASPHALT COATINGS, COMPRISING: COATING BASE GRANULES WITH A COLORED COATING COMPOSITION COMPRISING WATER-SOLUBLE SODIUM SILICATE CONVERTING THE SILICATE TO INSOLUBLE SILICA AT A TEMPERATURE NOT ABOVE ABOUT 600* F. AND WITHOUT REMOVING THE SMALL BUT APPRECIABLE AMOUNT OF WATER-SOLUBLE MATERIAL REMAINING AFTER SUCH CONVERSION; AND APPLYING TO THE HYDROPHILIC SURFACE OF THE RESULTANT GRANULES A THIN COATING OF A SOLUTION IN A HYDROCARBON OF A SUBSTITUTED SILICANE CAPABLE OF MOLECULAR ORIENTATION WITH RESPECT TO A HYDROPHILIC MINERAL SURFACE SAID SILICANE BEING SELECTED FROM THE GROUP CONSISTING OF ALKYL, ARYL, ALKOXY AND ARYLOXY SILICANES CONTAINING AT LEAST ONE READILY HYDROXLYZABLE INORGANIC RADICAL ATTACHED TO SILICON. 